Process for making magnesium silicate products



N. GOODWIN 2,203,614 PROCESS FOR MAKING MAGNESIUM SILICATE PRODUCTS June 4, 1940.

Filed May 6, 1950 SQ@ m TTORNE Y PatentedL June 4, `1940 UNITED STATES PATENToi-FICE 2,203,614 p PROCESS Fon MAKING MAGNESIUM- j SILICATE PRODUCTS Norris Goodwin, Long Beach,`alif., assigner, `by mesne assignments, to Hewlings Mum'perand Lewis Cruickshank, Los Angeles, Calif:`

Application May 6,1930, seriaL1"Nc.l450,155

claims.

This invention relates to a process of treating natural magnesium carbonate-containing minerals with silica, and has for its principal object the production of carbon dioxide in large quan- ,5 tities in a simple, novel and highly efllcient manner, `as `wellI as the production of magnesium silicate in essentially colloidal form which may be valuable as a pigmentor as a filler for rubber, or wherever a finely divided, surface re-` but all such attempts have heretofore failed due to the fact that when magnesite (MgCOa) is heated sufficiently to give olf CO2, an equilibrium is established in the reaction'as follows:

MgCOaMgO-I-COZ it will be noted Vthat the reaction proceeds in both directions and is. never .complete in` the direction from left to right as long as the reaction is carried out in an atmosphere of CO2, due to4 partial` pressure effects and the greater the partial pressure of C012 in the reaction vessel, the

n right. 0

The` effect of this is that all attempts toproduce CO2 by this reaction have resulted not only in the incomplete production. of CO2, `but also` in the production of MgO which is not market- Mgooa+sio2+H2o=magnesium siiicate+oo2 The correct formula for the silicate thus formed is not definitely known, but it is probably in a hydrated form. The reaction is `essentially magnesium carbonates when proper temperature and pressure conditions are used.

Magnesium silicates formed by the above reaction are in a finely divided colloidal condition and have important uses aspigments, catalysts,

adsorptive agents, bleaching material, heat in sulators, emulsiiers, and may in fact be `used wherever finely divided colloidal materials can` be applied in variousarts.

00 Withrefererice to the drawing, in which Fig. 1

A further object is to `produce a magnesium;

less complete will be the reaction from left to` able due to sever contamination with MgCOa.

complete from left to right and is common to all isa diagrammatic ow sheet, Fig. 2 is a longitudinal vertical section of a heater, and Fig. 3 is aivertical sectional `view of a cooler, the natural magnesium carbonatecontaining material, such as magnesium carbonate, 4hydrated magnesium carbonate, basic magnesium carbonate, or the like, together with siliceous material, such as diatomaceous earth, quartz,'opaline silica, or the like, is supplied through a hopper Ill'into any well known form` of grinder I I, such as a ball mill, `or the like, water being added through a pipe I2; I I

`The grinding `operation is contained until a slurry is former in which the magnesium car-` bonate-containing mineral is reduced to l a particle size not greater than ,100 mesh, and preferably to` a size such as to pass through a 300 mesh screen, which slurry is forced by a pump I3 through pipe Minto a heater I5.

The size to which the carbonate containing mineral is reduced depends on the reactivity of the same and on the subsequent temperature and pressure used as well as the time of application. The 4ilner the material is ground, the more surface is available for reaction and therefore less time, temperature andpressure will be required to complete the reaction.

Heater 4I5 has an outer shell I6 and an inner shell` Il, inlet pipe I4 being welded, or otherwise securely fixed to shells I6 and Il, outlet pipe I3 being fastenedthereto in like manner. An inlet pipe I9 `and an outlet pipe 20 provide for the continuous introduction and discharge of a heating medium, such` as hot oil, between and through tures and pressures are produced in the slurry in shell Il.V Shell I'I has a series of vertical transe` partments formed bythe ballles in shell Il by` means of an4 inlet 25 and a discharge 26. for heating the slurry. The temperature of the slurry is indicated by a pyrometer 27 and the pressure by a gage 28,`and carbon dioxide and steam pass out fof pipe 23 to a reflux refrigerator, or con.- denser 30, wherein any steam` is condensed to fall back into shell I1, while the dry carbon dioxide will `pass through pipe 3l and regulating valve 32 to be stored in container 33.

The` magnesium silicate `and water will pass through pipe I8, regulating valve 35, and pipe 34 into a dryer 36 whence the dried silicate may be shellsylli andII whereby the` reaction tempera-r withdrawn through pipe 31 while vapor will pass out of pipe 38.

In operation, depending on the raw carbonate used, 'or the metal silicate desiredtherefrom for any particular purpose, the pressure and corresponding temperature of steam at that pressure, in shell Il will be regulated `to the end desired. For instance, in using magnesite (MgCO3) as a raw material, pressures of from 500 pounds up to 1000 pounds per square inch;

or higher, are highly desirable, inasmuch as the carbon dioxide will becompletely driven oli'in the reaction yielding a magnesium silicate having highly advantageous bleaching properties.

Pressures as low as 150 pounds per square inchr may lbe used, but thereaction period is then so slow as to be entirely uncommercial inasmuch as the time required lto complete the reaction willv be beyond commercial limits and thecourse of the reaction from left to right as indicated above will not approach completion. On the other hand the high pressures not only give the desired speed of reaction, but give a conversion entirely `continuous stream of CO2.

unknown before. l

`A certain amount of agitation may be desirablein shell Il and this is provided by the spacing of baffles 2l and 22 in accordance with the velocity of the 'flow of thel slurry, but other well known forms of mechanical agitators may be provided as Well. Hence, it will be clear that the4 slurry, or mixture of finely ground materialsI with water or aqueous fluid, is maintained from pump I3 through heater'l to regulating valve 35, and consequently the steam in heater I5` must be saturated steamat a temperature in` excess of 212 F. at any superatmospheric pressure employed.

It is, of course, obvious that the carbon dioxide may be passed under its'self-generated, or auto- 'I genous, pressure from the line 3| into the containers, or `steel cylinders 33, of which there may be a plurality thus eiecting a large saving and efiiciency'over known methods of storing gases under pressure wherein a compressor and extra equipment must be used. p

The process is obviously designed for Acon-- tinuous operation due to the fact that purnpl3 continuously forcesthe slurry into shell I 'l where its temperature under a desired pressure ismain- :tained by the continuous introduction and discharge of the heating mediumy to and from pipes I3 and 20 while baffles 2| serve tol agitate the slurry in accordanceVV with its velocity through shell Il. The velocity of the slurry depends on the speed of pump I3 in operating against the pressure `controlled by regulating valves 32 and 35, regulating valve 35 being opened a sufficient'V amount to permit the continuous passage of a `mixture of the magnesium silicate and water nesium silicate and water which is unvapvorizedk at the given pressure as well as the continuous withdrawal of CO2 through pipe y3|; said pressure being vinitially controlled by regulating valves 32and35. n n v vsaid mineral substance is eliminated and at least a ymajorportion of the magnesia content of said magnesium carbonate is converted to magnesium silicate.

' 2. A' process for making a magnesium silicate' vproduct which comprises rgrinding a natural magnesium carbonate-containing mineral sub stance to a particle size not greater than about V300' mesh and heating the nely divided mineral sub--l stance with iinely divided silica.y and water inv `the form of a slurry at a temperature equivalent to a steam pressure of at least about 500 pounds per square inch until'at least a major portion of the carbon dioxide content of thev magnesium carbonate in said mineral'substance is eliminated and at least a major portion of the'magnesia content of said magnesium carbonate is converted to magnesium silicate.

` 3. A process for'making a magnesium silicate product which ycomprises grinding a" natural magnesite to a particle size not greater than about 300 mesh and heating'the `finely divided magnesite withnely divided silica and waterin the form of a slurry at a temperature equivalent to a steam pressure greatly in excess of lpounds per square inch and not substantially below the neighborhood of 500 pounds per square inch until at least a major portion of the carbon dioxide content of the magnesite iseliminated and at least a major portion of the magnesia con-'- tent ofA the magnesite is converted to magnesium silicate.

4. A process for making a magnesium silicate product which comprises grinding au natural magnesite to a particle size not greater than about'300 mesh and heating the iinely divided magnesite with nely divided silica and water in the form of a slurry at a temperature effective to produce a pressure of fromabout 500 to '1000 pounds per square inch until at least a major portion of the carbon dioxide content of the magnesite is eliminated and at least a major portion of the magnesia content o f the magnesite is converted to magnesiuml silicate.

5. A process for making a magnesiumsilicateV product which comprises vgrinding a natural magnesium carbonate-containing mineral substance to a particle size not greater than about 300 mesh, heating the nely divided mineral substance with nely divided silica and water in the form of a slurry at a temperature equivalent to a steam pressure greatly in excess of 150'pounds per square inch and not substantially below the neighborhood of' 500 pounds per square inch and removing carbon dioxide during said heating until'at least amajor portion of the carbon dioxide content of the magnesium carbonate in said mineral substance is eliminated and at .least a major portion of the magnesia content of said magnesium carbonate is `converted to magnesium silicate. l NORRIS GOODWIN. 

